Detection of suspended matter in gases



' June 13, 1950 A. H. HOBELMANN DETECTION 0F' SUSPENDED MATTER IN GASES Filed May 25, 194e PA ssi/v60? @Mm/WMM III Patented June 13, 1950 DETECTION OF SUSPENDED yIVIATTER, IN GASES .Alfred H. Hobemann, Chevy Chase, Md., as-

signor to Specialties Development Corporation, BloomfielcLeN. J., a corporation of New Jersey Application YMay `25, 1946, Serial N0.*6'72,`207

6 Claims. :1 This invention'relates to improvements Yin apparatus for detecting suspended matter in fluids.

While the present invention has many applications, it is particularly well'adapted -for the detection and comparison of smoke-laden air from different sources, whereby the presence of fire at its source can readily be detected and an alarm given. Accordingly, such application o1' adaptation of the invention will be referred to herein for convenience of description and villustration.

In smoke detecting apparatus, Aas is now well known, air is continuously ldrawn from the :protected area or space to a smoke detecting cabinet where the presence of smoke in the air is detected by either or both visual and audible means. In such apparatus. a conduitleads `directly from the protected area or space to the -smoke detecting cabinet.

However, in some installations, the protected space receives air from another space or spaces, usually adjoining compartments, so that the air drawn from any one of Vthose compartments to a smoke detecting cabinet is not representative of the air in thatl compartment,'but is a combination or mixture of the air from the communicating compartments. Undersuch circumstances, it is impossible to determine the exact source of smoke. A specific illustration of suchv an installation is in aircraft Where the ventilating system draws air from a passenger vcompart- 'men''tc and through a cargo compartment. It is apparent that if passengers in the passenger compartment are smoking, the smoke will be drawn into the cargo compartment, thence through the conduit leading from' the cargo compartment to the smoke detecting cabinet, causing false indication of re in the cargo compartment with resultant confusion.

One of the objects of the present invention `resides in the provision vof apparatus whereby under such conditions as mentioned, theipresence of smoke in the cargo'compartme'nt originating,

'by reason of passengers smoking in a communivemitted by passengers in a ycommunicating com- .partment nAnother object of vrthe A.present invention re- -sides in thesampling of airfrom communicat- 2 .ing compartments or protected areas- .'and loom'- paring the density of the samples, wherebyV to determine, when smoke is present therein, whether the sa-me is the result of fire or merely incidental to passengers smoking.

A further object of the present invention re- .fsides in the provision of :apparatus `of the character lindicated which readily can `be installed and which may operate in conjunction with air circulating systems generally employed.

.Further objects, not specifically enumerated above, will be apparent as the invention is 'des scribed in greater detail in connection with the vaccompanying drawing, wherein:

Figure l is a diagrammatic view of an apparatus rfor carrying out the present invention.

.Figure '2f is a schematic fragmentary view of ya fuselage of van vairplane having apparatus in accordance with the :present invention installed therein.

Figure 3 is a wiring diagram suitable for use ywith the present invention.

Referring to the drawing in detail, the ap"- Vparatus illustrated in Figure 1 is a vsmoke ydetector of novel construction comprising a pair of hollow tubes vI0 Yand I2, a' housing I4 for a light source 116, mirrors I8 and 20` and vother elements, as will be described presently.v

This smoke detector is adapted to be mounted at a suitable location in a cargo compartment 22, as shown in: Figure 2. As will be seen from Figure 2, the cargo compartment- 2'2 is situated below a passenger compartment 24, theoor of which is provided with openings- 26 leading to 'a duct 28+having lan open` end 29- extending into .the cargo Acompartment 2-2.v A conduit 30 leads 'from-one end-of -the-.duct-28 to-an inlet 32 Yof the tube Ill ofthe smoke detector. The tube H1.' has an outlet conduit -3-l provided witha suction-'fan 33 -for drawing -air `from the vduct 2-8 Athrough the tube lll `by way' of the inlet-32.

A blower 34 is mounted in the cargoV compart- -ment`2i2 adjacent the airfoutlet-therefromf. This blower isprovidedwith an 'inlet 36- whereby fair 'is drawn'ffrom the compartment 22v and forced through 'a conduit 38 into the tube I2-of the lsmokedetectorfby way oi inlet 40,. thence ethrough the tube and out by way-of afcond-uitffinto .an exhaust conduitl.

lAdjacentV tor-thel cargo compartment 22.1is Ianother compartment 42 which houses equipment for maintainingthe air in vthe passenger com- -partment-under pressure. This equipment .may be the conventional airrecirculating equipment :havinga blower 44 `which-,draws air fromthe passenger compartment by way of duct 28 and outlet 29 into the cargo compartment 22 and through inlet conduit 46 of blower 44. The air drawn by the blower 44 from compartments 22 and 24, in the manner just described, may be passed to the atmosphere, or all or part of it may be cleaned, ltered and otherwise treated and then recirculated to the passenger compartment.

During operation of the air circulating system and the smoke detector, a sample of the passenger compartment air is continuously drawn through the tube, while a sample of the combined passenger and cargo compartment air is drawn through the tube I2. When conditions are normal in the cargo compartment, that is, no smoke is being generated therein due to a nre, the samples of air passing through the tubes IU and I2 will be of the same quality.

The smoke detector automatically compares; the density of suspended matter in the air in the tube I with that in the tube I2. This is accomplished by means of a normally balanced electrical bridge circuit including light sensitive elements and a galvanometer type relay as diy agrammatically illustrated in Figure 3. The tubes I0 and I2 are each provided at one end with a photoelectric cell of the current generating type 6U and 62 respectively, and at their other ends with lenses GI and 63 respectively, which are so mounted as to hermetically seal the ends of the tubes.

When no smoke is present in the tubes I0 and I2, light from the light source I6 is transmitted equally tc the cells E0 and 62 by the mirrors- IB and 20, through the lenses 6I and 63 and tubes I0 and I2 respectively, and the bridge remains balanced. However, when smoke enters the tube I0 from the passenger compartment, the intensity of the light reaching the photoelectric cell G9 will be reduced, whereby the bridge will be unbalanced and current will flow in one direction through relay 64 enclosed in the housing I4, deflecting the needle 66 to the left, as viewed in Figure 3. When smoke, originating in the passenger compartment and passing into the cargo compartment by way of duct 28, passes from the cargo compartment 22 into the tube I2, the density of the smoke in each tube will be substantially equalized whereupon the needle will return to its normal position of balance as shown in Figure 3.

Should a iire occur in the cargo compartment the smoke enters the tube I2 and the intensity of the light reaching the cell '62 will be reduced to a greater extent than that of the light reaching the cell S, whereby current will be caused to ilow through the relay S4 in the opposite direction, which will result in the needle 66 being deflected to the right, as viewed in Figure 3, into engagement with contact 'It to close a circuit to the alarm 12.

It will be appreciated from the foregoing that when the smoke-laden air in the tube I0, received from the passenger compartment, is of the greater density, the needle 66 will be deflectecl to the left as viewed in Figure 3, and no Valarm will be given, whereas when the density in the tube I2 is the greater, the needle will be deflected to the right and will close the alarm circuit.

It will be seen from the foregoing that should passengers in the passenger compartment be smoking, the smoke-laden air which is drawn into the cargo compartment will not of itself operate the alarm, inasmuch as the smoke pass'- ing through the sampling conduit 30 and the tube I0 will be of greater density than the smoke passing directly to the cargo compartment out of the open end of the duct 28, the latter smoke being mixed with the air in the cargo compartment. However, when a re develops in the cargo compartment, the smoke drawn through the tube I2 from the cargo compartment will be of greater density than the sample of smokev leaving the passenger compartment, so that there will be a comparison of the density of the smoke passing through the tubes I0 and I2, and when this comparison indicates that the smoke in the tube I2 is of the greater density then, and only then, will an alarm be given. It is to be understood that instead of an audible alarm as illustrated visual detection of any of the conventional types may be substituted if desired.

While I have illustrated and described a preferred embodiment of my invention, it is to be understood that I do not wish to be limited to the 4precise structure and arrangement illustrated and described, as obviously various changes and modifications may `be made therein without departing from the spirit and scope of my invention.

I claim:

1. In a smoke detecting system, the combination of a pair of compartments one of which normally may contain smoke and the other of Which is supervised to detect the generation of smoke therein due to a re, means including a duct for exhausting air from the .first mentioned compartment through the second mentioned compartment, means for withdrawing a sample of air from said rst compartment, means for detecting the presence of smoke in the sample of air withdrawn from said irst compartment, means for withdrawing a sample of air from said second compartment, means for detecting the presence of smoke in the sample of air withdrawn from said second compartment, and means for giving an indication when the density of the smoke in the sample withdrawn from said second compartment exceeds the density of the smoke in the sample withdrawn :from said rst compartment.

2. In an airplane smoke detecting system, the combination of a passenger compartment, a cargo compartment, means including a duct for exhausting air from the passenger compartment through the cargo compartment, means for withdrawing a sample of air from the passenger compartment, means for detecting the presence of smoke in the passenger compartment air, means for withdrawing a sample of air from the cargo compartment, means for detecting the presence of smoke in the cargo compartment air, and means for giving an indication when the density of smoke in the cargo compartment air exceeds the density of smoke in the passenger compartment air.

3. In an airplane having a passenger compartment, a cargo compartment and means for withdrawing air from the passenger compartment to the cargo compartment including an air duct leading from the passenger compartment to the cargo compartment, the combination of sampling means for receiving a sample of the air withdrawn from the passenger compartment, sampling means for receiving a sample of the air withdrawn from the cargo compartment, a light source, means for directing light rays from said source into said sampling means, a light sensitive element associated with each of said sampling means and located in the path of said light rays, electrically operated means responsive to said elements, and a signal circuit adapted to be closed by said electrically operated means when the density of suspended matter in the air in a predetermined one of said sampling means exceeds the density of the suspended matter in the air in another of said sampling means Suniciently to set up a differential in the intensity of the light rays falling on said light sensitive elements.

4. In an apparatus for detecting the presence of fire in a compartment through the detection of smoke originating therein, which rst named compartment is functionally in communication with a compartment in which smoke may be present, and which is subject to a flow of air from the second named compartment, the combination of a pair of receivers, means for withdrawing a sample of air from the rst named compartment through one receiver, means for withdrawing a sample of air from the second named compartment through the other receiver, and means associated with the receivers for indicating an increase of density of smoke in the sample of air from the rst named compartment over the density of smoke from the second named compartment due to the presence of re in the rst named compartment and the increased production of smoke therein.

5. In an apparatus for detecting the presence of re in a compartment through the detection of smoke originating therein, which compartment is functionally in communication with a second compartment in which smoke may be present, and which first named compartment is subject to a iiow of fluid from the second named compartment, the combination of means for withdrawing fluid from the second named compartment to the rst named compartment to provide a mixture of the fiuid of both compartments in the first named compartment, a pair of receivers, means for withdrawing a sample of the mixture of fluid from the iirst named compartment through one receiver, means for withdrawing a sample of nuid from the second named compartment through the other receiver, and means associated with the receivers for indicating an increase in the density of the fluid from the first named compartment over the density of fluid from the second named compartment due to the presence of re in the rst named compartment and the increased production of smoke therein.

6. In an apparatus for detecting the presence of re in a compartment through the detection oi smoke originating therein, which compartment is functionally in communication with a second compartment in which smoke may be present, and which first named compartment is subject to a dow of air from the second named compartment, the combination of a conduit leading from the second named compartment to the rst named compartment, suction means for withdrawing air from the second named cornpartment to the iirst named compartment to provide a mixture of the air of both compartments in the rst named compartment, a pair of receivers in said first named compartment, means for withdrawing a sample of the mixture of air from rst named compartment through one receiver, means for withdrawing a sample of air from the second named compartment through the other receiver, and means associated with the receivers for indicating an increase of density of smoke in the sample of air from the first named compartment over the density of smoke from the second named compartment due to the presence of nre in the first named compartment and the increased production of smoke therein.

ALFRED H. HOBELMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 878,456 Darwin Feb. 4, 1908 2,437,071 Cahusac et al Mar. 2, 1948 FOREIGN PATENTS Number Country Date 788,111 France July 22, 1935 OTHER REFERENCES Article on page 131, of Helios, published April 23, 1933. 

